Climate expert highlights need for rain-resilient cities

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With the intensification of climate change and the acceleration of urbanization, extreme weather disasters around the world pose serious challenges to urban security and economic development. In particular, the frequency of severe rainfall events in various places has increased, threatening urban security.

Professor Li Yongkun, director of the Institute of Disaster Prevention and Mitigation at the Beijing Institute of Water Science and Technology (BWSTI), recently gave an interview to talk about how to make super-large cities with frequent severe rainstorms safer and more resilient.

Professor Li is mainly engaged in the research of basic theory and applied technology of urban flood prevention and mitigation. He has undertaken more than 30 national scientific research and technical consulting projects, published more than 40 papers, and authorized more than 20 invention or utility model patents and software copyrights.

His research achievements have won four provincial and ministerial awards including the Beijing Science and Technology Progress Award and the Beijing Agricultural Technology Promotion Award.

Question: How has the global climate changed in recent years? Why does climate change exacerbate natural disasters?

Professor Li: In recent years, the global climate has changed drastically. According to “Climate Change 2023”, the sixth comprehensive assessment report released by the United Nations Intergovernmental Panel on Climate Change (IPCC) in March this year, the global surface temperature from 2011 to 2020 increased by 1.1 degrees Celsius compared with pre-industrial levels. This has not only resulted in more frequent and intense extreme weather events, but has also brought about increasing threats to nature and humans in every region of the globe, posing serious challenges to ecosystems and human health.

The impact of climate change on flooding is particularly complex. On the one hand, drastic changes in the frequency and intensity of rainstorms directly change the input conditions of floods; on the other hand, the urbanization process changes the types of underlying surfaces such as vegetation and soil, which intensifies soil erosion, leading to an increase in flood peak flow, resulting in concurrent torrents and debris. The risk of major floods continues to rise.

At the same time, super-large cities have high population density, complex economic activities, and large-scale development of underground space, resulting in limited space for storing flood water, significant urban “rain island effect” and “heat island effect”, and drastic changes in the characteristics of flow generation and confluence.

Extreme rainstorm events in super-large cities are generally sudden, including large-scale floods, mountain torrents, mudslides, waterlogging, and have aggregation, chain, and amplification effects, which not only threaten people’s safety and property, but also lead to the paralysis of modern service networks such as communications, electricity, and transportation, posing a great threat to the operation of cities.

Question: In recent years, how have super-large cities around the world dealt with disasters caused by heavy rain?

Professor Li: London, New York, Seoul and Beijing have all experienced extreme rainfall in recent years. Megacities around the world have accumulated a lot of experience in dealing with such disasters.

For example, the Netherlands, Germany, Austria and other countries have adopted multifunctional flood control projects and established a socialized disaster prevention system in which the government, society, and families work together.

Through the use of new technologies such as big data, the capabilities of comprehensive perception, accurate forecasting and early warning, operation scheduling, and emergency response have been improved.

These measures aim to improve a city’s ability to respond to natural disasters such as extreme rainstorms and floods, reduce the loss of life and damage to property caused by disasters, ensure the smooth operation of the city, and provide guarantees for future sustainable development.

Question: How can urban planning and construction techniques be used to build more resilient cities? How can we protect a city when a disaster strikes?

Professor Li: Urban resilience refers to a city’s ability to maintain basic functions and quickly return to normal operations in the face of various pressures and shocks.

It involves many aspects such as urban planning, infrastructure construction, emergency response mechanisms, post-disaster assessment and recovery.

In terms of hardware construction, it involves water conservancy infrastructure such as reservoirs, dikes, sluices, and pumping stations, as well as storage spaces such as green spaces, lakes, and ponds.

The strengthening of these hardware facilities can ensure proactive comprehensive defense in advance before and during disasters, cutting off the connection between disaster-causing factors and disaster-affected bodies, thereby reducing the impact of disasters on cities.

In terms of software, it involves emergency plans, emergency response mechanisms, dispatching decision support systems. These software measures can ensure that in the event of an emergency, the city can quickly coordinate, respond and rescue, and minimize losses.